1. My enemy's enemy is not my friend.
If you need proof try Osama bin-laden.
Both Iran and ISIS chant the same tune -- "Death to America!" Right now, they are in a struggle for regional dominance. When their struggle is over the victor will chant death to America again.
Why the USA negotiates with doorknobs and demagogues like those leaders in North Korea and Iran is beyond me.
North Korea:
https://www.armscontrol.org/factsheets/6partytalks 2002 and still talking ...